Such a resonant trap is known from the international application WO03/025608. The known resonant trap has a cylindrical arrangement with an inner conductor and an outer conductor. Both are connected to each other at the resonant trap's shorted end. The inner conductor covers part of the electrical lead and the outer conductor covers the inner conductor. The known resonant trap has a channel trough which a cable or electrical lead can be fed by simply sliding it through the channel. In particular no galvanic connection is needed between the resonance trap and the cable or electrical lead.